This invention relates to methods for treating psoriasis.
Psoriasis is a chronic skin disorder that afflicts about 2 percent of the population. Classic psoriasis--called plaque psoriasis--commonly appears as inflamed swollen skin lesions covered with silvery white scale. Psoriasis can manifest itself in blistering (pustular psoriasis), severe sloughing of the skin (erythrodermic psoriasis), drop-like dotting (guttate psoriasis) or smooth inflamed lesions (inverse psoriasis). About 150,000 to 250,000 new cases of psoriasis are diagnosed each year. Psoriasis most commonly appears on the scalp, knees, elbows, hands and feet, but can affect any part of the skin. It can be very painful and psychologically devastating. The cause of the disease is unknown, though it is believed to have a genetic component, and may be an autoimmune skin disorder.
There is no cure for psoriasis, presently, although there are various treatments with varying degrees of success. Current treatments can temporarily clear the plaques and significantly improve skin appearance. However, symptoms return once the therapies are discontinued. Thus, therapy must be resumed when the psoriasis returns.
The treatment employed depends upon psoriasis type, its location on the body, and its severity, as well as the patient's age and medical history. Most of the common therapies involve topically or orally administered compositions. Generally, the more effective such compositions are--particularly against severe forms of the disease, the greater the typc and frequency of their side effects.
For example, topical steroids are one of the most common therapies in mild to moderate cases. However, even topical steriods have side effects--which typically arise from over use--including skin thinning, stretch marks, and a resistance to the medications which causes them to become ineffective.
Systemic steroids--an injectable form of steroids--are another treatment, which involves injecting steroids into the lesion(s). This treatment is impractical when there are many lesions since many injections would be required. Oral doses or muscular injections of steroid medications to treat patients with many lesions are not recommended because of side effects. Occasionally, the withdrawal of steroids may be associated with a worsening or flare of psoriasis and long-term use can create serious side effects.
Topically applied coal tar can improve the skin's appearance, but it is unpleasant and may make the skin more sensitive to ultraviolet light. Thus, extreme caution is advised when combining its use with UV therapy (or exposure to the sun) in order to avoid severe burns.
Anthralin--a topically applied compound--can irritate or burn normal appearing skin surrounding psoriasis lesions and can stain anything it comes into contact with.
Retinoids, both topical and oral, also have been employed to treat psoriasis. Tazarotene, a topically applied retinoid, can cause skin irritation, which occurs in almost 40 percent of patients.
Oral retinoids (e.g. soritane and tegison) have even worse side effects, and therefore are used only in severe cases that do not respond to other therapies. Soriatane has the virually invariable risk of birth defects to developing fetuses if the mother is using the drug. In fact, women are counseled to avoid pregnancy for three years after the drug is discontinued. Women taking tegison are counseled to avoid pregnancy both during and indefinitely after treatment because tegison can cause severe birth defects long after its use.
Women who use soriatane must not drink alcohol during treatment and for two months after therapy is discontinued. Alcohol can cause Soriatane to be metabolized to tegison in the bloodstream, leading to tegison-type side effects.
Cyclosporin has been given to patients with severe forms of psoriasis, but it is only indicated for severe psoriasis since the drug--originally developed as a immunosuppressant (to prevent organ transplant rejection)--obviously should not be administered to patients who can benefit from other psoriasis therapies.
Methotrexate can be given either as a pill or by injection for psoriasis or psoriatic arthritis. However, it has short and long-term side effects. Short-term side effects can include nausea, fatigue, loss of appetite, and less frequently, mouth sores. Long-term use of methotrexate can lead to liver complications and necessitate a liver biopsy to make sure that the liver is tolerating the drug.
Phototherapy--medically supervised administration of ultraviolet light B--is used to control widespread or localized areas of stubborn and unmanageable psoriasis lesions, when topical treatments have failed, or it is used in combination with topical treatments. The long-term risks of UVB skin cancer and skin aging.
Photochemotherapy (PUVA) (an acronym for the combination of the drug Psoralen with UltraViolet A Light) is used to treat moderate to severe psoriasis, as well as disabling psoriasis that cannot be controlled by other means. The drug psoralen is activated by the skin's exposure to ultraviolet light (UVA). PUVA can be used to treat the whole body or specific skin sites such as the hands and feet. It can also be combined with other psoriasis therapies. The most common short-term side effects of PUVA are nausea, itching and redness of the skin. Long-term use of PUVA can cause freckles and/or experiencing premature aging of the skin, as well as cataracts. Long-term PUVA also increases the risk of skin cancer. Thus, PUVA is only recommended for people who have psoriasis on over 30 percent of their bodies, or for those who have not improved on other therapies.
As should be apparent, while many therapies have been used to treat psoriasis, individual therapies, particularly for severe cases have limitations either with efficacy or with side effects. Thus, there is a need for improved therapies for psoriasis with fewer side effects.